The patch for LU-5573 (http://review.whamcloud.com/#/c/12353/), which closed LU-5299, does not cover some cases.

Specifically, the code which enables the combined MGT/MDT to start correctly also disables the race protection for a combined MGT/MDT.

So racing multiple mount commands on a combined MGT/MDT can still cause this problem.

I've taken a look, and I don't see any easy way to fix this in the current context. I can provide dumps if needed, and I'll attach a log now.

Note the attempts to start MDT0000. There are five, four of which start after the first one but before it has completed.